UV light blocking and conversion by porous europium-doped titanium dioxide (TiO₂-Eu) thin films for potential protection of photovoltaic devices

In recent years, transparent thin films capable of screening and converting ultraviolet (UV) photons into visible spectrum gained significant interest in the protection of photovoltaic devices. We investigated the optical properties and UV screening capability of europium-doped titanium oxide (TiO₂−Eu) thin films deposited by the spin-coating method from a solution precursor for the first time in this study. We showed that TiO₂-Eu thin films demonstrate europium concentration-dependent optical properties, and the quantum yield of the optimized sample was found to be ∼10.2%. Transmittance and photoluminescence measurements suggested that TiO₂−Eu thin film can effectively block UV photons (∼30.5% at 320 nm) at glass substrate and convert them to the red emission thanks to ⁵D₀ →⁷F_j (j = 0, 1, 2, 3, and 4) Eu (III) electronic transitions. Photodegradation experiments with methylene blue dye revealed that TiO₂−Eu thin films offer better UV protection compared to uncoated samples. We strongly believe that porous TiO₂−Eu thin films can be effectively utilized as a UV blocking and light conversion coating.